Booster



Dec. 26, 1967 J. J. MINNICK ETAI- 3,359,902.

BOOSTER I Filed Dec. 27, 1965 Y 2 Sheets-Sheet 1 22 I5 F G. 4

F G 2 JOSEPH J.M|NN|CK ROY O sARsON '3 INVENToRs.

By 444%) M d 3M ATTORN EYS Dec. 26, 1967 J. J- M|NN|K ETAL 3,359,902

BOOSTER Filed Dec. 27, 1965 2 Sheets-Sheet 2 fg; E Fl G 8 l?,

n s Q 2o JOSEPH J. MINNICK u ROY D. sARsoN 22 30 l5 INVENTORS.

BY /f/ud/ m f ATTORNEYS United States Patent Oice 3,359,92 Patented Dec. 26, 1967 3,359,902 BOOSTER Joseph J. Minnick, Terre Haute, Ind., and Roy D. Sarson, Marion, Ill. (both Commercial Solvents Corporation, Terre Haute, Ind.)

Filed Dec. 27, 1965, Ser. No. 516,394 5 Claims. (Cl. 102-24) ABSTRACT 0F THE DISCLOSURE A booster for detonating insensitive blasting charges having a specially placed core of Primacord-sensitive explosive material encased Within a sheath of relatively insensitive explosive material of high brisance.

This invention relates to detonating means for relatively insensitive explosives and, more particularly, to boosters for insensitive explosives wherein high intensity shock effects are obtained by the interaction and reinforcement of detonation Waves within the booster.

In recent years insensitive explosives, eg., those containing a high percentage of ammonium nitrate suitably mixed With explosive or non-explosive organic sensitizers, have found Widespread application by military and commercial consumers as blasting explosives. Such insensitive explosive compositions generally are characterized by their inability to be detonated by blasting caps necessitating the utilization of dynamite or ne grained TNT asa primer to initiate detonation. Because primers of this nature are both expensive and extremely hazardous, the explosive industry in recent years has turned to boosters utilizing a core of Primacord-sensitive explosive material surrounded by a compacted sheath of Primacordinsensitive explosive material of high brisance, such as are described in Cook et al. U.S. Patent No. 3,037,453, issued June 5, 1962. That patent describes boosters having one or more perforations adapted to receive a detonating fuse extending through the sheath of Primacord-insensitive material and communicating with the Primacord-sensitive material forming the inner core of the booster to produce upon ignition a chain of detonations beginning with the detonating fuse and extending sequentially to the Primacord-sensitive explosive material and the Primacord-insensitive material. Such prior art devices, however, are deficient in that they require two detonating fuses to ignite the Primacordsensitive core When such core is Wound in a compact figureeight configuration. The utilization of dual detonating fuses is presumably to obtain a maximum detonation velocity and, coincident therewith, a maximum of brisance. When a single detonating fuse is employed, prior art devices generally are forced to forego the benefits of a lfigure eight configuration and rely upon a more extensive helical wrapping of the Primacord-sensitive explosive material.

Applicants have discovered a unique method of winding tubular Primacord-sensitive explosive material into a plurality of superimposed loops as a core within a sheathing of Primacord-insensitive material to obtain a maximum of detonating pressure from a minimum of tubular explosive material by utilization of the scientific principles embodied Within the Dautriche method of measuring velocity of detonation. The Dautriche method contemplates the ignition, simultaneously or sequentially, of both ends of a tubular length of explosive material to produce explosive waves propagating in opposite directions along the length of tubular material. At the point and instant of intersection of the explosive shock waves, there is such interaction and reinforcement of the individual Waves as to produce a high intensity shock effect far in excess of the algebraic combination of the dual waves.

In order to make maximum utilization of the shock eect produced by the reinforcement of the explosive waves, applicants form a unitary length of tubular Primacord-sensitive explosive material into a series of superimposed loops extending radially outwardly from a point approximately centrally located within the booster. A single perforation adapted to receive a detonating fuse is provided extending through the relatively insensitive outer sheath to communicate with the Primacord-sensitive explosive core at the point of intersection of the necks of the superimposed loops. Thus, the loops are ignited by a single detonating fuse and the explosive waves propagate outwardly from a single point along two distinct loops of the tubular material toward a position intermediate the length of each loop Where a reinforcement of the explosive Waves produces a high intensity shock effect to detonate the surrounding sheath of insensitive material.

Two distinct configurations are contemplated for forming the superimposed outwardly extending loops necessary for the proper operation of this invention. The first is generally a ligure eight adaptation wherein the two ends of the tubular explosive forming the neck of the loop cross one upon the other, While in the second configuration the neck of each loop is formed by abutting a unitary piece of tubular explosive along its length so that the ends forming the neck are at the same horizontal level. With either configuration, the outwardly extending loops should be geometrical equivalents symetrically disposed about a center point located at the point of intersection ofthe necks, the loops extending substantially perpendicularly outwardly from a plane parallel to said perforation passing through the perforation and said necks.

With geometrically equivalent loops and uniformity of composition along the length of the tubular explosive such that identical rates of wave propagation are produced, each of the radially extending loops at a particular level will generate a reinforced shock wave simultaneously. Thus, a maximum shock wave reinforcement is obtained both by the unique geometric configuration employed in Winding the tubular Primacord-sensitive explosive core as well as the centrally positioned detonating fuse producing uniformity of detonation. By obtaining a maximum of interaction between the generated shock Waves of the tubular core a minimum amount of expensive Primacord-sensitive material need be utilized and a substantial reduction in the cost of the booster is achieved.

In a further embodiment of this invention, the Primacord-sensitive explosive material is imbedded within a layer of explosive material the sensitivity of which lies intermediate the Primacord-sensitive material and the Primacord-insensitive sheath. Thus the intermediately sensitive explosive material functions as a booster for the high brisance insensitive sheathing which composes the main explosive charge of the booster.

It is, therefore, an object to this invention to provide a unique geometrical Winding configuration for the tubular, highly sensitive explosive core of a booster to obtain a maximum shock effect from a minimum of explosive material.

It is a further object of this invention to provide a booster wherein a layer of intermediately sensitive explosive is employed as a booster for the main explosive charge of the booster. Y

A more complete understanding of the basic principles of this invention can be obtained by reference to the appended drawings in which:

FIGURE l depicts an exploded isometric view of a booster wound in accordance with this invention.

FIGURE 2 is a plane view of a completed booster in accordance with this invention with the top removed.

FIGURE 3 is an assembled cross-sectional view of the booster of this invention taken along lines 3-3 of FIG- URE 2 upon removal from its base.

FIGURE 4 depicts a booster in accordance with this invention wherein the explosive core is threaded through the central perforation.

FIGURE 5 is an alternate means of winding the explosive core.

FIGURE 6 is a plane view of an assembled alternate embodiment of FIGURE 5.

FIGURE 7 is a cross-sectional View taken along line 7"7 of FIGURE 6 and FIGURE 8 is a cross-sectional view similar to FIG- URE 7 but includes an intermediate sensitive secondary booster.

Referring more particularly to FIGURES l, 2 and 3 a pair of vertically upstanding rods 11 and 12 function as a support to retain tubular Primacord-sensitive explosive material 13 in an elevated position relative to hase 14 and bottom cover 15 which subsequently act as supporting surfaces during the molding of the booster 16. Tubular material 13 can be fabricated from any of the Primacord-sensitive explosive materials presently available including pentaerythritol tetranitrate (PETN), cyclotrimethylenetrinitramine (RDX), tetranitromethylaniline (tetryl) etc. and is wound in a generally figure eight configuration with loops 17 and 17a extending perpendicularly outward from the vertical plane formed by upstanding rods 11 and 12. Each of loops 17 and 17a are symmetrically disposed relative to the vertical plane of rods 11 and 12 with the necks of all loops formed by crossing the ends of each loop one upon the other being vertically aligned within the plane. Thus, the symmetrical disposition of the core windings insures a simultaneous meeting and reinforcement of the detonation waves propagated along each level of loops 17 and 17a when ignition occurs at the necks of the superimposed loops. A pair of apertures 25 and 26 in bottom cover 15 are positioned in alignment with bores 27 and 28 Within base 14 to receive and securely position upstanding rods 11 and 12 respectively.

After core 13 has been satisfactorily wound, a cylindrical mold 18 is placed about the periphery of the core with its lower end positioned in circular ledge 19 formed within base 14. Molten Primacord-insensitive explosive material of high brisance 20, e.g., cast or pressed TNT, composition B (59% RDX, 40% TNT and 1% wax) or a mixture thereof, is poured into the mold to a level approximately .5 inch above the elevation of rod 11 and permitted to solidify. Rod 12, which is of a greater height than adjacent rod 11, will normally protrude above the surface of the molten mixture to provide a perforation 21 extending through booster 15 upon removal of the hardened explosive from the mold. The perforation 22 formed by rod 11, however, only extends a majority of the elevation of booster 16, terminating approximately .25 inch from the upper extremity of the booster. Upon completion of the filling of cylindrical mold 18 with the molten Primacord-insensitive explosive sheath 20, circular top 23 is applied as a protective covering to completely enclose booster 16 with upstanding rod 12 passing through central aperture 24 within top 23. In those situations when the cylindrical molds are fabricated from cardboard, paper or plastic, it has generally been found unnecessary to remove the solidified booster from the mold.

The finished product depicted in FIGURE 3 preferably is two inches in height and three inches in diameter with perforation being located at the geometric center of the cylindrically shaped booster. Perforation 22 is spaced approximately .25 inch from perforation 21, e.g., such distance as to permit a length of 50 grain reinforced Primacord to be snugly positioned between upstanding rods 11 and 12 when wound in a figure eight configuration and extends from the base to within .25 inch of the upper extremity of the booster. Thus, only centrally located perforation 21 extends the entire length of booster 16. Three complete figure eight Wrappings (or six loops) of 50 grain reinforced Primacord centrally positioned within the booster and extending to within .5 inch from the top and bottom have been found sufficient to detonate a surrounding layer of composition B.

The detonating fuse utilized in this invention can be a blasting cap positioned within perforation 21 or, if desired, the Primacord core can be extended upwardly through perforation 21, as shown in the embodiment depicted in FIGURE 4, to communicate externally of booster 16 thereby permitting electrical initiation of the central core 13 Without difficulty.

FIGURES 5, 6 and 7 portray an alternate method of winding the core of Primacord-sensitive explosive wherein the necks 30 of each loop are formed by abutting the tubular explosive along its length rather than crossing the ends of each loop as in the figure eight configuration. Because the only variation between the booster depicted in FIGURES l, 2 and 3 and the booster of FIGURES 5, 6 and 7 resides in the Amethod of winding the explosive core, corresponding parts are marked with identical reference numerals. It will be noted that the abutting method of Winding (or bow tie configuration) produces a series of superimposed loops 31 and 31a symmetrically disposed about the plane formed by upstanding rods 11 and 12 to permit simultaneous meeting and reinforcement of the explosive waves propagated along `loops 31 and 31a when the core is ignited at the necks of the loops. Because there is no overlap in this type of winding as compared with the figure eight winding, the central core 32 becomes more compact requiring slightly less vertical area within booster 15. The lateral distance between upstanding rods 11 and 12 must be sufficiently increased over the mold of FIGURE 1 to permit the tubular explosive to lie in juxtaposition intermediate the rods. Vertical perforation 21 extending the length of boster 16 is adapted to receive a detonating fuse in the form of either a blasting cap or Primacord. Thus, initiation of detonation occurs at the junction of the necks 30 of the oppositely extending loops 31 and 31a to produce two shock waves traversing each loop respectively in opposite directions. The waves along each loop interact and are reinforced according to the Dautriche principle simultaneously to produce high intensity shock effects resulting in far greater detonation pressure than is available with boosters having even a minute time interval between reinforced explosions.

Because there is no requirement to wrap the tubular explosive core about upstanding stakes 11 and 12, either winding configuration of this invention can be performed without the mold and retained in position by a layer of tape wrapped about the necks of the loops thus permitting greater speed and economy of manufacture. The wound core is then inserted between the upstanding stakes and the outer sheathing formed about it to produce the finished booster.

Referring more particularly to the booster depicted in FIGURE 8, the Primacord-sensitive explosive core 32 is imbedded within a layer of explosive material 33 having a sensitivity intermediate that of the core 32 and the relatively insensitive outer sheathing 20. Thus, layer 33 acts as an intermediate booster having suflicient sensitivity to be detonated by the interaction and reinforcement of the shock waves of explosive core 32 to produce an explosive pressure of such intensity to detonate outer relatively insensitive sheath 20. ith a booster arrangement of the type disclosed in FIGURE 8, considerable savings in the number of turns of relatively expensive tubular explosive required for detonation is achieved. Another advantage of the booster of this invention is that it permits the use of an outer sheathing material having a lower sensitivity than generally recognized as being necessary for such boosters.

We claim:

1. In a booster for detonating insensitive blasting charges having a core of Primacord-sensitive explosive material encased within a sheath of relatively insensitive explosive material of high brisance, said booster having at least one perforation adapted to receive a detonating fuse and extending through said sheath, the improvement comprising the formation of said core material into a configuration with two series of superimposed loops which extend outwardly from the perforation in different directions with the outward portion of the loops embedded within the relatively insensitive explosive material of high brisance whereby there are no voids adjacent said outward portion of the loops, the necks of which loops converge closely `adjacent said perforation, said loops extending substantially perpendicularly outwardly from a plane parallel to said perforation and passing through each perforation and said necks.

2. A booster according to claim 1 whenin said core material is encased within a layer of intermediately sensitive explosive material.

3. A booster according to claim 1 wherein said core material is additionally threaded through said perforation to function as a detonating fuse.

4. A booster according to claim 1 wherein said core material is pentaerythritol tetranitrate in tubular form.

5. A booster according to claim 1 wherein said core material is cyclotrimethylenetrinitramine in tubular form.

References Cited UNITED STATES PATENTS 6/ 1962 Cook et al. 102-24 10/ 1965 Lawrence 102-24 

1. IN A BOOSTER FOR DETONATING INSENSITIVE BLASTING CHARGES HAVING A CORE OF PRIMACORD-SENSITIVE EXPLOSIVE MATERIAL ENCASED WITHIN A SHEATH OF RELATIVELY INSENSITIVE EXPLOSIVE MATERIAL OF HIGH BRISANCE, SAID BOOSTER HAVING AT LEAST ONE PERFORATION ADAPTED TO RECEIVE A DETONATING FUSE AND EXTENDING THROUGH SAID SHEATH, THE IMPROVEMENT COMPRISING THE FORMATION OF SAID CORE MATERIAL INTO A CONFIGURATION WITH TWO SERIES OF SUPERIMPOSED LOOPS WHICH EXTEND OUTWARDLY FROM THE PERFORATION IN DIFFERENT DIRECTIONS WITH THE OUTWARD PORTION OF THE LOOPS EMBEDDED WITHIN THE RELATIVELY INSENSITIVE EXPLOSIVE MATERIAL OF HIGH BRISANCE WHEREBY THERE ARE NO VOIDS ADJACENT SAID OUTWARD PORTION OF THE LOOPS, THE NECKS OF WHICH LOOPS CONVERGE CLOSELY ADJACENT SAID PERFORATION, SAID LOOPS EXTENDING SUBSTANTIALLY PERPENDICULARLY OUTWARDLY FROM A PLANE PARALLEL TO SAID PERFORATION AND PASSING THROUGH EACH PERFORATION AND SAID NECKS. 